Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
A SUSPENSION DEVICE FOR A VEHICLE WHEEL
Document Type and Number:
WIPO Patent Application WO/2006/008564
Kind Code:
A1
Abstract:
The invention refers to a suspension device for a vehicle wheel, comprising a pen­dulum arm coupled, on the one hand, to a chassis of said vehicle by a first coupling means and, on the other hand, to said wheel by a second coupling means.

Inventors:
PEDERSEN ROALD H (NO)
Application Number:
PCT/IB2004/002015
Publication Date:
January 26, 2006
Filing Date:
June 17, 2004
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
PEDERSEN ROALD H (NO)
International Classes:
B60G3/14; B60G3/24; B60G7/02; B62D9/00; B62K25/00; (IPC1-7): B60G7/02; B60G3/14; B60G3/24; B62D9/00; B62K25/00
Domestic Patent References:
WO1988001576A11988-03-10
WO2004056645A12004-07-08
WO2002058277A12002-07-25
WO2001039127A12001-05-31
Foreign References:
US3177965A1965-04-13
DE3324665A11985-01-17
EP0569275A11993-11-10
US3899037A1975-08-12
EP0070025A21983-01-19
US4715615A1987-12-29
FR2559103A11985-08-09
Other References:
PATENT ABSTRACTS OF JAPAN vol. 012, no. 014 (M - 659) 16 January 1988 (1988-01-16)
Download PDF:
Claims:
CLAIMS
1. A suspension device for a vehicle wheel, comprising a pendulum arm coupled, on the one hand, to a chassis of said vehicle by a first coupling means, and, on the other hand, to said wheel by a second coupling means, characterized in that said first coupling means has a first swivel axis transverse to a vertical plane parallel to a forward direction of said vehicle, and a second swivel axis transverse to a hori¬ zontal plane, wherein said first swivel axis is not perpendicular to said vertical plane but inclined relative to a normal line of said vertical plane.
2. The suspension device according to claim 1 , characterized in that an inclination an gle of said first swivel axis relative to said normal line is 2 to 30 degrees as seen from above and/or is 0 to 5 degrees as seen in said forward direction.
3. The suspension device according to claim 1 or 2, characterized in that said first cou¬ pling means is positioned between two vertical planes defining said wheel on inner and outer sides thereof.
4. The suspension device according to any preceding claim, characterized in that a crossing point of said first and second swivel axes is positioned in a vertical mid plane of said wheel.
5. The suspension device according to any preceding claim, characterized in that said first coupling means is a cardan joint.
6. The suspension device according to any preceding claim, characterized in that said first coupling means is pretensioned axially and/or radially with view to at least one of said swivel axes.
7. The suspension device according to any preceding claim, characterized by a track width defining means coupled, on the one hand, to said chassis by means of a third coupling means, and, on the other hand, to said wheel by a fourth coupling means, wherein said third coupling means has a swivel axis transverse to a vertical line, and a straight line through said first and third coupling means is inclined relative to a normal line to said vertical plane.
8. The suspension device according to claim 7, characterized in that an inclination an¬ gle of said straight line is 4 to 45 degrees as seen from above and/or is 0 to 10 de grees as seen in said forward direction.
9. The suspension device according to claim 7 or 8, characterized in that said track width defining means comprises a lateral rod.
10. The suspension device according to any of claims 7 to 9, characterized in that said track width defining means comprises a driven or nondriven shaft of said wheel.
11. The suspension device according to any of claims 7 to 10, characterized in that said track width defining means are adjustable to vary a track width of said vehicle.
12. The suspension device according to any of claims 7 to 11 , characterized by a steer¬ ing rod for steering said wheel, wherein a joint connecting said steering rod to a steering mechanism is positioned on or in the vicinity of said straight line.
Description:
A SUSPENSION DEVICE FOR A VEHICLE WHEEL

The invention relates to a suspension device for a vehicle wheel, comprising a pen¬ dulum arm coupled, on the one hand, to a chassis of said vehicle by a first coupling means, and, on the other hand, to said wheel by a second coupling means.

The invention is about a new type of wheel suspension for vehicles, particularly pas¬ senger and utility vehicles. It enables a range of desirable functional characteristics to be achieved with a simple mechanism, in a space- and cost-saving manner. The suspension mechanism is particularly useful for a rear wheel suspension, both in the case when the rear wheels are driven, and not. The suspension may however also be used for a front pair of wheels which also have the option of being driven or non-driven. Prior Art

Here the description will be biased somewhat towards rear wheel suspensions. Over a period of more than one hundred years, rear wheel suspensions have evolved from stiff axles - which are still being used somewhat - in different fixation arrangements, to semi- independent or independent arrangements, such as:

- Torsion beam suspension which may be regarded as "half independent" due to the wheels in some respects being coupled together as on a stiff axle, in other respects however working independently.

Swing axle arrangements - where the wheels are fixed to transverse suspension mem¬ bers which rotate around axes extending in the longitudinal direction of the vehicle.

- Trailing arm suspensions where a suspension arm extending from the wheel forward in the longitudinal direction of the vehicle is fixed to the vehicle chassis rotatably around axes perpendicular to the mid-plane of the vehicle.

Semi-trailing arm suspensions fixed to the chassis rotatably around axes which are at an angle to a line perpendicular to the mid-plane of the vehicle.

- The "Weissach axle" which may be regarded as a further development of the semi- trailing arm suspension, introducing a joint to achieve more desirable functional charac¬ teristics.

- The MacPherson, sometimes called the "Chapman strut" suspension, where the wheel is attached to the sliding suspension damping element which again is fixed to the chas¬ sis as well as being controlled by a suspension arm or a combination of arms and rods.

- The double wishbone suspension, where the wheel is fixed to a carrier (upright), which is rotatably fixed to a pair of high and low placed transverse suspension arms which again are rotatably fixed to the chassis. - The multi-link suspensions which in the recent years are prevailing more and more. Here the wheel is attached to a carrier which is linked to the vehicle by three, four or five suspension arms and rods in different configurations.

- The publication FR 2 559 103 deals with a front wheel suspension for a light passenger vehicle where the wheels are fixed to arms which are swung sideways for the purpose of steering and simultaneously displacing the center of gravity of the vehicle to stabilize it in a curve.

Problems with Prior Art Solutions

The influence of the wheel suspension on the driving characteristics of a vehicle is complex, and involves a range of parameters, functions and effects coming together. The wheel, thus the wheel suspension, relates both to the ground and to the vehicle, which also relates to the ground. There are kinematic, kinetic, linear and non-linear effects relating to the influence on, as well as the influence from, the suspension system in the environment ground - wheel - suspension and vehicle.

From here on, with reference to figure 1 , the description deals with three major func- tional characteristics of a wheel suspension:

- The camber angle y of the wheel (wheel lean) relating to the vertical axis of the vehicle.

- The steered direction v of the wheel ("toe in" or "toe out"). It is understood that here, the "steer angle" of a pair of rear wheels is dealing with small deviations from the straight ahead direction such as less than one or two degrees.

- The track width b between the mid-planes of a pair of wheels.

These three characteristics are prescribed by the kinematic conditions of the wheel suspension mechanism when the wheel is moving vertically, compounded with other influ¬ ences. Out of these the description particularly deals with the effects due to the wheel being subjected to the following:

- A braking force - A side force such as when negotiating a curve - A traction force

It is understood that when said characteristics, when influenced by said conditions, are within their desired intervals, the wheel suspension is functioning well. The expression "jounce" (bump) refers to the situation where the wheel is forced upwards such as when hitting a bump or the vehicle leans (rolls) in a curve. "Rebound" refers to the opposite situa¬ tion where the wheel suspension is extended downwards from its nominal position such as when the wheel is hitting a pot hole or the vehicle rolls in a curve.

The roll center M defines the point around which, for each pair of wheels, the vehicle tends to start to lean when entering a curve. The roll center for a semi-trailing arm suspen¬ sion is defined as shown in the figure. The semi-dotted line marked CL defines the center of the vehicle. The axis through the roll centers near the front pair of wheels and the rear pair of wheels for a four-wheeled vehicle is termed the roll axis for the complete vehicle. The following is a brief summary of the relevant characteristics of the hitherto known wheel sus¬ pensions:

Stiff axles have the benefits of a fixed track, are however associated with a high un¬ sprung mass which have to follow the wheel during vertical movements. Furthermore the individual camber and steer angles (toe in - toe out) of each wheel are fixed to each other, thus limiting the freedom of the mechanism to tune said angles individually to each other for each wheel during vertical wheel movements. Another negative aspect is that whenever one wheel is subjected to movements, such as when on bump, the other wheel is also affected due to the wheels being interconnected. Therefore, stiff axles are today less common than earlier.

- The torsion beam suspension is so configured, that when one wheel is subjected to a vertical movement, the other will partly be forced in the same direction, in this manner thus reducing body roll in a curve. However, wheel camber is more or less constant during jounce and rebound. When subjected to a side force, the suspension tends to deflect so that the wheel steers towards the force, which is undesirable as it makes the vehicle self steer into a curve. In other words this tends to make the vehicle "oversteer" in certain situations - which is an undesirable, unstable characteristic. This tendency may be minimized by attaching the suspension to the vehicle with resilient bushings with certain characteristics, this however may bring other undesirable effects by its own. Lately, the torsion beam suspension is somewhat less used, being replaced by other types.

- The swing axles have long since been abolished due, among other things, to their radi¬ cal change of wheel camber during bump and rebound movements, in combination with a rather high roll center.

- The trailing arm suspension has a constant track, however no change of camber during vertical movements, and a low roll center. When influenced by a side force, they will tend to steer on par with the torsion beam suspension.

- The semi-trailing arm suspension, as shown in figure 1 , prevailed for a long time as a much used rear wheel suspension, particularly for rear wheel driven vehicles. This sus¬ pension may be regarded as a cross between the swing axle and the trailing arm vari¬ ants. Here the angle α represents the component of the angle between a swivel axis and a perpendicular line to the mid-plane of the vehicle as seen in a top view, whereas β represents the same in a rear view. By combining a good geometry with a good choice of the angles α and β, the suspension may yield good camber angle- and steer angle change functions during the vertical wheel movements, combined with a good roll center height. Depending on the magnitude of α and β, the track b between the wheels varies during said wheel movements. However, one of the major drawbacks of this sus¬ pension mechanism is that the wheel will steer outwards (toe out) during braking and when suddenly backing off a drive power, and, particularly, steer towards a side force which acts upon the wheel. These characteristics may all compound towards creating an oversteering effect, and they will all be exaggerated by the (common) use of resilient bushings in the fixation of the suspension arms to the chassis.

Therefore, semi-trailing arm suspensions have by now more or less been abandoned by the automotive industry.

- The "Weissach" axle introduced a resilient joint into the trailing arm suspension, making the wheel steer "toe in" particularly during braking. To some extent this improved the behaviour of the suspension. However, the characteristics of the extra joint introduced some problems of its own, and the Weissach suspension is no longer used.

- The MacPherson (or Chapman strut) suspension, commonly in a configuration where the damper extends upwards beyond the top of the wheel, and has the suspension spring situated around the top of the damper, builds quite tall. It can be shown that there are some limitations regarding the geometry which may be used. The forces of the wheel induce bending moments in the sliding connection in the damper, leading to stic- tion, thus unwanted resistance against vertical wheel movements. The tendency now is that this type of suspension is less used for the front wheels of vehicles, and particularly for the rear wheels of vehicles.

- The double wishbone or multi-link suspensions provide high degrees of freedom to con¬ figure camber angle-, steer angle- and track width change during the vertical wheel movements. In parallel these suspensions may be configured to display good geometric behaviour when subjected to forces on the wheel. Being built up of many parts, they are however costly and complex as well as bulky (space demanding) - particularly in the lat¬ eral and vertical direction of the vehicle. It is known that when this suspension is config¬ ured into a small space, this increases the reaction forces on the joints of the mecha¬ nism. This again limits the endurance of the joints, and makes the wheel being less pre- cisely guided when wear of the joints eventually takes place, to the detriment of the wheel governing function of the mechanism. - The proposal in FR 2 559 103 is made particularly for the purpose of achieving a trans¬ fer of weight simultaneously with steering a small vehicle, and is limited to this particular application.

- PCT/IB02/05833 "Vehicle", PCT/IB03/02148 "Drive System for a Wheel" and PCT/IB2004/001757 "Snowmobile" by the same inventor show the usage of certain elements such as suspension arms and their attachments and guidance for the purpose of providing suspension mechanisms for ground-engaging means for tilting vehicles.

The purpose of this invention is to allow a new type of wheel suspension, which, although it has good functional characteristics, is simpler, less costly and less space- demanding than the alternative wheel suspensions such as the multi-link type.

According to the invention, the above purpose is achieved by a suspension device for a vehicle wheel, comprising a pendulum arm coupled, on the one hand, to a chassis of said vehicle by first coupling means, and, on the other hand, to said wheel by a second coupling means, characterized in that said first coupling means has a first swivel axis trans¬ verse to a vertical plane parallel to a forward direction of said vehicle, and a second swivel axis transverse to a horizontal plane, wherein said first swivel axis is not perpendicular to said vertical plane, but inclined relative to a normal line to said vertical plane.

In other words, the above purpose can be achieved through replacing some suspen¬ sion members such as arms (links), struts and uprights (hub carriers), with joints with other constraints than hitherto used for this purpose, in combination with orientating said joint as well as other suspension support members so that optimum functional characteristics are achieved.

The invention enables camber angle- and steer angle change as a function of the vertical wheel movements on par with the best wheel suspensions used today, in combina- tion with good response characteristics to external forces on the wheel. It will however do with a smaller number of parts for this purpose, and with less use of space. Conversely, it provides the functional benefits of the trailing arm suspension, without the negative effects of this, when being subjected to external forces and changes of these. Preferably, an inclination angle of said first swivel axis relative so said normal line is 2 to 30 degrees as seen from above and/or is 0 to 5 degrees as seen in said forward direc¬ tion.

According to a particularly preferred embodiment of the invention, said first coupling means is positioned between 2 vertical planes defining said wheel on inner and outer sides thereof. Thereby, acceleration and braking forces do not or to a very small extent influence the wheel orientation.

Ideally, a crossing point of said first and second swivel axes is positioned in a verti¬ cal mid-plane of said wheel.

According to a most preferred embodiment of the invention, said first coupling means is a cardan joint.

Said first coupling means is preferably pre-tensioned axially and/or radially with view to at least one of said swivel axes. Thereby, the orientation of the wheel can be defined by said pendulum arm very precisely.

Preferably, a track width defining means coupled, on the one hand, to said chassis by means of a third coupling means, and, on the other hand, to said wheel by a fourth cou¬ pling means is provided for wherein said third coupling means has a swivel axis transverse to a vertical line, and a straight line through said first and third coupling means is inclined relative to a normal line to said vertical plane.

It is understood, that said track width defining means are meant for taking lateral forces acting on the wheel and, thereby, defining the position of the wheel in a direction transverse to a vertical plane lying parallel to the forward direction of the vehicle.

According to a particularly preferred embodiment of the invention, an inclination an¬ gle of said straight line is 4 to 45 degrees as seen from above and/or is 0 to 10 degrees as seen in said forward direction. Said track width defining means may comprise a lateral rod.

Alternatively or in addition, said track width defining means comprises a driven or non-driven shaft of said wheel.

Preferably, said track width defining means is adjustable to vary a track width of said vehicle.

The invention is applicable not only to suspensions for non-steered wheels, but also to suspensions for steered wheels. Therefore, what is preferably provided for is a steering rod for steering said wheel, wherein a joint connecting said steering rod to a steering mechanism is positioned on or in the vicinity of said straight line.

Thereby, a so-called "zero bump steer" may be achieved.

The following is a detailed description of preferred embodiments of the invention, referring to the drawings, in which

figure 1 is a perspective view of a semi-trailing arm sus- pension according to the prior art,

figure 2 is a perspective view of a first embodiment of the invention,

figure 3 is a view of the suspension according to figure 2, but taken from above,

figure 4 is a top view of 2 further embodiments of the invention,

figures 5 and 6 are perspective views of 2 further embodiments of the invention,

figure 7 is a perspective view of a still further embodi- ment of the invention, and

figure 8 is a top view of the embodiment according to figure 7. Figure 2 shows a perspective view of the right hand side of a rear wheel suspension without drive for a vehicle, whereas figure 3 shows a top view of the same mechanism. 1 indicates the suspension arm upon which the stub axle 3 is fixed around which the wheel 24 revolves. 2 denounces the subframe to which the suspension arm is fixed through the means of the cardan joint 13. The subframe is attached to the vehicle through the resilient insulation elements 4. The cardan joint may be specified to have its bearings somewhat pre-tensioned both radially and axially. Its bearings can equally be specified to take high loads in both said directions. In this way the joint will be able to transmit and endure large forces in all directions. It is also understood that a cardan joint is defined through providing angular freedom around two axes perpendicular to - and intersecting - each other. Now it is equally understood that a joint consisting of two axes more or less transverse to each other as well as not quite intersecting each other provides a similar functionality.

Now it is furthermore understood that any such configured joint is within the scope of this invention.

As seen in the top view of figure 3, the axis 5 of the cardan joint is at an angle α1 to a line perpendicular to the mid-plane of the vehicle. As seen in figure 2, said axis may also be at an angle β1 to said line as seen in the front or back view of the vehicle. The figure shows a lateral rod 6, fixed to the sub frame or other parts of the chassis of the vehicle through a pin - or a spherical - or a resilient joint, supporting the suspension arm through a similar joint.

The rod is shown attached in the position a). However, the dotted lines indicate the alternative positions b) and c) of this rod.

As seen in the figures, the axis 8 is intersecting the cardan joint and the fixation joint between the lateral rod and the subframe or chassis. As can be seen, the alternative posi¬ tions, such as the position b), influences the angle α2 towards the line perpendicular to the mid-plane of the vehicle. A corresponding angle β2 can again be defined as seen in the front or rear view of the vehicle.

Now the following is realized: When the wheel moves up or down, due to negotiating a bump, a pothole or a curve or a combination of said influences, the sideways position of the wheel is determined by the support rod 6 and its position, together with the overall geometry of the suspension. The freedom of the suspension arm to follow said rod results in small movements around the axis 7 of the cardan joint. In some geometrical configurations of the dimensions and the angles, the joint will adapt by moving simultaneously around both axis 7 and 5. It is now clear that the steer angle of the wheel (toe in or toe out) as well as the track between the centers of two wheels are functions of said lateral position of the wheel in any vertical wheel position, thus are defined by the lateral rod 6. In effect the center of the wheel can be said to revolve around the axis 8 in this respect.

Now it is also realized that the camber angle Y of the wheel in any vertical position is a function of the angles α1 and β1 together with the overall geometry of the suspension. It can be shown that the first angle usually will be much greater than the second one, and that the first angle will influence the camber angle more than the other.

Now it is furthermore realized that the track between the mid-planes of the wheels where they intersect the ground is compounded by components resulting from the camber angles of the wheels, the other components being the lateral positions of the wheels them- selves as defined as said.

It can be shown that it is possible to arrange an overall geometry of the suspension which can provide the desired camber angle and steer angle functions for the wheel during its vertical movements. This typically means the wheel going slightly into negative camber (leaning towards the car) on bump (jounce), and slightly into positive camber on rebound.

The optimum steer angle change is dependent on different factors, and may involve the wheel to steer slightly in (toe in) during bump, and slightly out (toe out) during rebound. However, there are vehicles where the opposite effect is wanted, possibly also going first to toe out then towards toe in during bump. It can be shown that with this mechanism, these steer functions can be achieved. As discussed, the track change will follow these functions. It can however be shown that for the practical geometries and angles to be used the track change during vertical wheel movements will be within reasonable limits.

Figure 4 shows a top view of the mechanism, where the left hand half figure shows the left hand suspension with the lateral rod 6 placed in position a). The right hand side suspension is supported by the lateral rod in position b) or c). The dotted lines of the wheels indicate the displacements of the wheel due to a braking force or a side force acting on them through their contact paths with the ground.

As can be seen, the left hand side configuration tends to make the wheel steer in a toe out direction. The subframe, due to its being fixed to the chassis by the resilient attach¬ ments, is also influenced. In the case of a braking force of the same magnitude acting upon both rear wheels, the subframe will be displaced backwards not influencing the toe out steer of the wheels any further.

In the case of a side force, however, the subframe will be displaced at an angle adding somewhat to the steered direction of the wheels.

This may in sum indicate that the position a) of the lateral rod is usually not the pre¬ ferred one.

The right hand side of the figure shows that with the rod in the position b), a much less influence of the lateral position of the wheel, thus the steered direction, is experienced during a side force or a brake force.

It is furthermore understood that the nearer the cardan joint is placed to the mid- plane of the wheel, the more braking force is taken up directly in that joint, straining and deflecting the lateral rod less, thus influencing the wheel position and direction correspond- ingly less. It is clear that if the joint is placed outside the mid-planes of the wheel, this will result in a toe in deflection of the mechanism during braking. It is also clear that position c) of the lateral rod will tend to provide a toe in response of the wheel when influenced by a side force. It can be demonstrated that in the case of a front or rear crash the S-shaped longitu¬ dinal suspension arms will deform in the longitudinal direction of the car by bending. It is clear that now, in this way, the vehicle has in effect got additional deformation members to take up energy in the case of a crash, compared to most other wheel suspensions. Now these crash forces are conveniently fed into the subframe, which again distributes the crash load contribution from said members to the vehicle on a broad basis, which is beneficial. It is furthermore clear that on most vehicles the position in height of said arms is lower than the main energy-absorbing structure, creating in effect a larger crash contact area, thus a less aggressive and penetrating vehicle in crash.

Figures 5 and 6 show perspective views of the rear wheel suspension configured for the situation where the rear wheels are driven.

In figure 5, 10 indicates the drive shaft being driven off the output shafts in the differ- ential housing 12. The shaft is fixed to the rotating wheel hub through the cardan joint 9, and correspondingly by the cardan joint 11 to the output shaft of the differential. It is under¬ stood that the axes of the two cardan joints may be at a 90 degrees angle to each other as shown, thus balancing out the cyclically varying rotational speeds of the joints when they work at angles.

As previously discussed, the cardan joint can be specified to take high loads as well as being precise. The joint rotating does not preclude that it serves as a lateral rod to sup¬ port the wheel. There is prior evidence of drive shafts with cardan joints serving as suspen¬ sion members for rear wheel driven vehicles, albeit in another type of wheel suspension.

It is also understood that both the wheel and differential bearings are of a sturdy type, such as conical roller bearings, which may be pre-tensioned axially to arrest the rotat¬ ing shafts axially. Being furthermore capable of transferring large axial loads, it is clear that said bearings provide ample support for the drive shaft for said use.

Figure 6 shows an alternative configuration, where the lateral rod 6 is employed to¬ gether with a driveshaft 10 which is thus relieved from carrying axial loads to support the wheel. This may then give greater freedom to define the position and dimensions of the lateral rod. In consequence, the driveshaft must now be somewhat axially floating in one end to absorb the different distances from the differential to the wheel during the vertical movements of the wheel. The drive shaft joints may be of the constant velocity type, and the inner one may conveniently be of the type which is axially floating, as commonly used on cars.

The kinematic and static and dynamic load effects as discussed for the solution in the previous figures prevail also for these two driven wheel suspensions. The traction of the wheel results in a force directed forward upon the wheel. Now it can be sown that a toe in- , toe out or neutral steer effect may correspondingly be achieved during traction influence.

It is realized that the steer direction as prescribed by the wheel suspension may at any time be overridden by controlling the length of the lateral rod or the position of its at¬ tachment to the chassis. The small adjustments needed for this can, for example, be in- duced through the means of adding an extendable element 16 to the rod. The length of this element may be electrically or hydraulically controlled, and governed to take place accord¬ ing to the needs of the situation. One example of this is to correct the course of the vehicle in the case that it is getting out of control.

Figure 7 shows a perspective view of the right hand side of a front wheel suspen¬ sion. The suspension is shown with a driven wheel, but may also be executed without drive.

Figure 8 displays a top view of the same suspension. In the figures, 17 indicates the front drive shaft in the case that the wheel is driven, 18 denounces the axis around which the front wheel is steered. The axis 18 is defined by a pin joint 15 in the suspension arm 1 which the suspension upright (hub carrier, steering knuckle) 19, thus the wheel, can revolve and be steered, around. It is now clear that from here on a distinction must be made be¬ tween the small steer effects resulting from the movements of the suspension, and the steered direction as induced on the wheel around axis 18 by the driver through the means of the steering rod 20 being actuated by the steering mechanism 21.

The joint connecting the steering rod to the steering mechanism is on or near the axis 8 which extends through the cardan joint and the fixation joint for the lateral rod. In this way there will be zero or very little steer reactions induced upon the wheel ("zero bump steer") during vertical wheel movements, due to the steering mechanism.

It is understood that the steering axis may be inclined both backwards (the caster angle) and inwards towards the vehicle (king pin- or steering axis inclination). The cardan joint 13 again fixes the suspension arm to the sub frame (engine cradle) 2, being arranged, together with the lateral rod 6, so that optimized angles α1 , α2, β1 and β2 are used (β1 and β2 not shown here). Following that the overall geometry also is optimized, similar charac¬ teristics as for the rear suspension may be achieved. It is clear that both the caster- and king pin inclination angles will change during vertical wheel movements. It is acknowledged that a large change of particularly the caster angle may be detrimental to such a steered wheel suspension. Extending the suspension arm in the longitudinal direction of the vehicle, possibly in combination with limiting the vertical wheel movements, will improve upon this situation.

It can be argued that this front suspension mechanism, with its space saving layout, may be particularly effective on small passenger and utility vehicles.

To sum up, the suspension mechanisms as shown provide good kinematic behav- iour together with good responses when subjected to static and dynamic loads. This is achieved with less suspension elements than hitherto for a similar performance, in a cost- and space saving manner.